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AC/DC Desktop adapter, non floating ground?

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Zero999:

--- Quote from: magic on September 12, 2019, 08:43:10 am ---Depends. It may only make it worse if the problem happens when ground bounces around due to Y capacitors while some high impedance signal nodes bounce at a lower amplitude due to capacitive coupling to ambient.
Electrostatic shields should be referenced to the ground of the circuit they protect.
--- End quote ---
I don't see how a shield can make it worse.

As long as the shield is connected to the supply rails, via a low impedance AC path and surrounds the low level signals, it will only improve things. The shield will form a Faraday cage, which can bounce up and down due to the Y capacitors, but as long as the circuit in side is referenced to it, there won't be any interference.

Someone:

--- Quote from: magic on September 12, 2019, 08:43:10 am ---
--- Quote from: ejeffrey on September 11, 2019, 04:25:22 pm ---A medical rated power supply will have less ground leakage so will likely be considerably better than standard industrial/telecom power supplies even when floating.
--- End quote ---
These are treacherous. They still have some capacitive injection of primary-side junk, their outputs are not grounded due to regulations, they look like they might be grounded because they have three-prong plugs, but that's actually because they are shielded to reduce EMI.
--- End quote ---
Not all medical standard mains supplies are floating, you can get them with the DC output connected through to the input earth.

TimNJ:
Hi James,

This power supply has a series impedance in the earth return path as you described above (Class II with functional earth):
https://www.digikey.com/product-detail/en/globtek-inc/TR9CI1500CCPIMR6B/1939-1768-ND/9837833

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